1. Field of the Invention
The present invention relates to an ophthalmic microscope.
2. Description of the Related Art
Various ophthalmic operations have been conventionally performed. In particular, cataract surgery is one example of an ophthalmic operation that has been typically performed. “Cataracts” is an ophthalmic disease, wherein the natural lens of the eye becomes clouded due to aging or other causes, leading to decreased visual performance. A procedure called phacoemulsification (hereinafter, referred to as “the suction method”) has been a commonly performed operation for cataracts. In the suction method, an incision is made along the edge of the cornea and the capsule, an aspirator is inserted into the incision to remove the clouded lens, and an intraocular lens (IOL) is implanted in place of the removed lens.
In the suction method, a surgical microscope is used to obtain an enlarged image of the patient's eye (hereinafter, referred to as “the operating eye”). In this case, transillumination (red reflex) has been widely utilized as one way of improving the visibility of the image. Transillumination is generated by diffusing the illumination of the surgical microscope and reflecting it onto the ocular fundus of the operating eye. In particular, this is extremely effective for confirming the location of the incision in the capsule in order to insert the aspirator, or for determining whether the clouded lens has been completely aspirated.
Various means have been conventionally proposed and implemented in order to obtain a preferred red reflex for the conductor of the surgery (hereinafter, referred to as “the operator”). A major example of such means includes “0° lighting” wherein a deflection mirror is placed between the right and left observation optical axis visible through a binocular surgical microscope in order to direct the illumination light to the operating eye along the optical axis of the objective lens, or a complete coaxial lighting wherein the optical axis of the illumination system (hereinafter, referred to as “the optical axis of the illumination light”) is directed by a half mirror along the optical axis of the observation system (hereinafter, referred to as “observation optical axis”).
However, in the case of 0° lighting, since the red reflex in the observation beam varies from right to left, there are problems in that, for example, the image is not favorably fused when viewing with binocular vision. In complete coaxis lighting, only a completely darkened image is obtained due to reduced amount of the observation light reflected by the half mirror. Thus, there is a problem of reduced visibility.
Therefore, a means called “angle lighting (slant lighting)” for illuminating at a certain angle to the observation optical axis has been widely employed. Conventional surgical microscopes employing angle lighting include, for example, that disclosed in Patent laid-open No. 2004-139002. Such a surgical microscope acts such that a partial area of the image where a red reflex cannot be obtained from a portion of the illumination light directed by one of paired deflection members is complemented by a red reflex obtained from the other portion of the illumination light directed by the other deflection member. Accordingly, a red reflex can be obtained across a wide range of the observable retina. In addition, a bright red reflex can be obtained by directing the illumination light to the operating eye simultaneously by a pair of deflection members.
Furthermore, an entity microscope is provided for conducting meticulous observation or photographing of the observation object, the patient's eye (hereinafter, referred to as “the inspecting eye”). For example, the microscope disclosed in Patent laid-open No. 2001-275978 is a known entity microscope that enables observation of the anterior and interior (the fundus) of the inspecting eye by inserting and removing the entity angle adjustment part on the right and left optical axis to change the entity angle. Such an entity microscope enables optimal observation and photographing or the like of the anterior, or fundus, of the inspecting eye promptly and easily by equipping the entity angle adjustment unit and the color temperature conversion element in order to transform the entity angle using the entity angle transformation unit depending on the observation of the anterior fundus of the eye, as well as to convert the correlated color temperature (the observed color (herein, “the color of the illumination light”) of the blackbody temperature, that is, the numeric indication of color).
However, as in the case of cataracts, when the degree of cloudiness (intensity of the reflected light) varies depending on the progression of the condition where cloudiness spreads over the lens, for example, in the case of hypermature cataracts, a red reflex cannot be obtained even with complete coaxis lighting. It is extremely difficult to perform CCC (Continuous Circular Capsulorrhoxis, i.e. incision of the capsule) without a red reflex. When performing CCC for cases of hypermature cataracts, a method has been employed for observing the light reflected from the capsule of the lens using angle lighting and a red reflex obtained by the complete coaxis lighting. However, since the capsule of the lens has extremely high transparency and low reflection intensity, it is difficult to obtain sufficient visibility. Consequently, utilizing the ability of the eyeball tissue to transmit long wavelength light favorably and to reflect short wavelength light relatively, a light source containing xenon light (hereinafter, referred to as “xenon light”) has been used. The xenon light features a correlated color temperature of approximately 6,000K, which is higher than that of the common halogen light source of microscopes.
On the other hand, for common cataract cases in which the condition has not progressed to this extent, that is, the lens has not clouded to such a degree (hereinafter, referred to as “common cataracts”), CCC can be effectively performed in the presence of a red reflex. However, in order to obtain a red reflex, an illumination light with a correlated color temperature of approximately 3,000K is required. Therefore, defects occur in microscopes employing a xenon light source.
As such, an ophthalmic microscope with complete coaxis lighting and angle lighting may have to be used depending on the medical condition, such as in the case of cataracts. Considering the purchase and maintenance cost of the device and the requirements for storage space, one device with multiple functions has been desired.
In addition, it is considered possible to prevent the above-mentioned problems by equipping the invention disclosed in Patent laid-open No. 2004-139002 with the invention disclosed in Patent laid-open No. 2001-275978, that is, equipping the conventionally existing filter mechanism with a correlated color temperature changing filter in order to change the correlated color temperature of the light source. However, it is difficult to say that the above problems can be completely prevented, since a changing operation or the like is still required. Furthermore, in order to reduce the burden on the operator or the conductor of the examination (hereinafter, referred to as “the examiner”) having to perform the operation over long periods of time or conducting examinations many times, such as in mass screenings, it is necessary to develop an ophthalmic microscope that enables the examiner to change the observation conditions with a simple adjustment.
Consequently, the present invention has been developed in consideration of such circumstances. The invention intends to provide an ophthalmic microscope that includes complete coaxis lighting and angle lighting to allow the observation conditions and the correlated color temperature to be changed easily and promptly.